AU2011201085B2

AU2011201085B2 - Manufacturing method for insulated flexible air ducts

Info

Publication number: AU2011201085B2
Application number: AU2011201085A
Authority: AU
Inventors: Graham David Palmer; Gregory William Palmer
Original assignee: PALTECH CORP Pty Ltd
Current assignee: PALTECH Corp Pty Ltd
Priority date: 2010-04-01
Filing date: 2011-03-10
Publication date: 2016-08-11
Anticipated expiration: 2031-03-10
Also published as: AU2011201085A1

Abstract

A method for manufacturing an insulated flexible air duct (10) is disclosed. The method includes providing a cylindrical inner core (12) having a central axis (A) and rotating the inner core about its central axis. A strip of insulation material (14) is fed onto the inner core (12), in a 5 direction substantially perpendicular to the central axis (A) of the inner core, whilst the inner core traverses in the axial direction. This results in helically overlapping multiple layers of the insulation strip whereby lateral portions (15) of successive revolutions overlap to create a continuous layer around the inner core. The speed of rotation and/or speed of axial traversal is able to be altered to provide the desired overlap distance of the lateral portions to create the ,0 overall thickness of the insulation layer for the individual ducts requirements. An outer layer (22) is then applied over the insulation layer. An insulated flexible air duct (10) is also provided. 3'2 Figure 3 F e Figure 4

Description

2

Manufacturing method for insulated flexible air ducts

Field of the invention

The present invention relates to a manufacturing method for flexible air ducts of the type that are insulated.

Background of the invention

Insulated flexible air duct is used to convey heated, cooled or ventilation air in heating, air conditioning and ventilation systems. Many processes have been developed for the fabrication of flexible duct beginning from the 1960's (for example US 3,216,459 to Pittsburgh Plate Glass Company). A common duct construction consists of three components: an inner core composed of helically wound polymer substrates bonded together with steel wire and adhesives or "interlock" polymer extrusions, a bulk insulation which is typically polyester fibre or glass wool, and an outer protective vapour barrier sleeve. The three components are typically assembled in a labour intensive operation in which the inner core is placed on an insulation blanket running the length of the inner core, which is dragged through a collar assembly onto which the outer sleeve has been fed, thereby attaching the outer sleeve to the outside of the insulated core, resulting in a single assembly. The blanket width is usually slightly wider than the circumference of the inner core to provide a small amount of fibre overlap to ensure that an insulation gap doesn't emerge along the longitudinal blanket seam, which would reduce the thermal resistance of the completed assembly. In practice, the sleeving operation tends to cause the seam to open up, contributing to a reduction in thermal resistance and an increase in energy loss in the heating or cooling system.

There have been some attempts to mechanise the process, while retaining the same components, thereby reducing the labour requirements (for example AU2001010018 to Anthony Tonna, AU2001100629, AU2006100893 and W02003/047979 to Westaflex (Australia) Pty Ltd).

Other construction techniques have been proposed in which the entire assembly is constructed in one pass, in which raw polyester fibre undergoes some processing adjacent to the duct equipment (for example US2008/0041483, US2008/0060713, AU2006252292, W02005/106315 to William Donnelly, and W02009/079719 to Nova-Duct Technologies Pty

Ltd), thereby reducing labour requirements and the cost of processed polyester fibre blanket. However, the complexity of forming ductwork dynamically, while injecting fibre in a highly controlled manner is extremely challenging, and requires complex control mechanisms, and costly, precision equipment To date, no single-pass process has been run commercially in Australia despite significant funding and early prototyping success demonstrating the principles.

Another single-pass process has been proposed (in US 5,607,529 to Adamczyk et al) in which a strip of fibrous insulation is helically wound around the core, followed by a helically wound outer sleeve. This process removes some of the difficult dynamic characteristics of the Donnelly and Nova-Duct processes, but introduces a number of new complexities. The process as described requires three independent operations, namely; inner core production, fibre application, and sleeve production, to be combined into one continuous operation with all processes operating simultaneously and at identical speeds. The process as described requires the helical pitch of all three components to be close to identical as the rotational velocity and axial velocities are identical, and matching the helical pitch on all three processes is a non-trivial exercise. A further challenge is the requirement to provide some overlap of the fibrous insulation, typically glass wool, so that no gaps appear in the insulation when the duct is bent, thereby providing a continuous helix of "double thickness" fibre, thereby resulting in substantial corrugations. For example, if 50mm thickness fibre is used, then most of the duct area will be 50mm thick, but a narrow 100mm thick helix will run continuously along the duct. It is not clear how the corrugations will be managed during the sleeve application stage as the sleeve may need to follow the continuous corrugation, or alternatively, the sleeve could be produced to fit the outside of the corrugation, thereby creating a large space in the majority of space within the corrugations. Either option may possibly render the resulting product unmarketable.

Flexible duct is available in typically 10 sizes and 3 insulation thicknesses, each requiring its own blanket specifications, therefore typically 30 types of blanket are used. Typical polyester batt production lines produce a range of insulation products, in a number of densities, thicknesses and widths. Accordingly, each product requires its own raw materials and settings, which need to be set for each new production batch. Insulation batts are very bulky, and need to be despatched regularly, and batt plants have limited capacity to store a buffer of inventory to allow flexibility in production schedules. Accordingly, the product type is constantly changing from shift to shift, and often within shifts, to cater for clients, who themselves have limited capacity to carry inventory and require a mix of products on a daily basis. The production of polyester blanket is prone to natural variability within the process, and the requirement to regularly change settings amplifies the pre-existing variability. In addition, many batt plants run 2 or 3 shifts per day, and maintaining production quality during night and evening shifts can present further challenges. A further challenge to fibre processing is the significant freight costs and warehousing requirements due to the bulkiness of the product. The requirement for a different blanket for each duct type necessitates very tight just-in-time inventory controls on raw materials for duct manufacturers and there is constant pressure on blanket suppliers to supply product daily. Occasional breakdowns or maintenance at batt plants can disrupt duct production and result in duct back-orders.

Advantageously, the proposed process aims to reduce the labour requirements significantly relative to the standard manual process and avoid the inherent problem of the insulation seam opening, avoid the technological and cost barriers to a Donnelly or Nova-Duct style single-pass process, and eliminate the practical weaknesses in the Adamczyk style process.

Reference to any prior art in the specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.

Summary of the invention

According to a first aspect, the present invention provides a method of manufacturing an insulated flexible air duct, including: providing a cylindrical inner core having a central axis; rotating the inner core about its central axis; feeding a strip of insulation material to the inner core, in a direction substantially perpendicular to the central axis of the inner core, whilst the inner core traverses in the axial direction thereby helically overlapping multiple layers of the insulation strip whereby lateral portions of successive revolutions overlap to create a continuous insulation layer around the inner core, such that the continuous insulation layer is built up by the multiple layers of insulation strip in any location along the length; wherein the speed of rotation and/or speed of axial traversal is able to be altered to provide the desired overlap distance of said lateral portions to create the required overall thickness of the insulation layer from multiple layers to meet the insulation requirement of the individual duct being manufactured; and applying an outer layer over the insulation layer.

Advantageously, the thickness of the insulation strip is the same for all duct sizes and insulation requirements, with the amount of overlapping providing the overall thickness of the insulation layer. At least three layers of insulation strip may be wound around the inner core in any one location along the length.

According to a second aspect, there is provided an insulated flexible air duct made in accordance with the first aspect of the invention.

According to a third aspect, there is provided an insulated flexible air duct, including: a cylindrical inner structural core; a continuous insulation layer created from helically wound and overlapping layers of a thin insulation strip whereby lateral portions of successive revolutions overlap to create the continuous insulation layer around the inner core; and an outer protective layer covering the insulation layer; wherein said overlapping lateral portions constitute a substantial portion of the width of the insulation strip, such that there are multiple layers of insulation strip at any given point along the length of the duct.

The number of layers of insulation strip around the inner core is preferably determined by the helical pitch of the insulation strip, which determines the resulting thickness of the insulation layer. The angular direction of the insulation strip with respect to the central axis of the inner core is substantially perpendicular, however, the angle may be adjustable to alter the pitch of the helical windings.

Preferably, the outer layer is provided by feeding the insulated core through a sleeving process whereby the insulated core is covered by a continuous sleeve layer. The protective layer is preferably a vapour jacket.

Advantageously, the lateral portions of the insulation strip are bonded together.

Advantageously, the insulation strip is a glass fibre insulation blanket.

Preferably, the cylindrical inner core is produced completely independently of the process for the application of the insulation layer.

The inner core preferably initially sits compressed between a rear head assembly and a front head assembly, whereby the rear and front head assemblies rotate in unison. The rear head assembly does not move in the axial direction. The front head assembly slides away from the rear head assembly dragging the inner core axially, extending it as the insulation strip is wound about it. A tray is provided to support the insulated core after it is wound and as it continues to slide away from the rear head assembly.

The diameter of the inner cores typically range between 100mm and 600mm. The width of the strip is typically in the range of 400mm to 600mm. Typically the thickness of the insulation strip is around 12mm. The overlapping lateral portions constitute a substantial portion of the width of the insulation strip. Typically this portion would constitute between 60-80% of the width of the insulation strip. This would advantageously result in at least three layers of insulation strip at any given point along the length of the duct. There may be as many as ten layers of the insulation strip.

Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

Brief description of the drawings

The present invention will now be described, with reference to the accompanying drawings, by way of example only, in which:

Figure 1 is a perspective front view of the inner core on a assembly device;

Figure 2 is a perspective front view of the inner core of Figure 1 partially extended and partially wrapped by the insulation layer;

Figure 3 is a perspective rear view of the assembly of Figure 2;

Figure 4 is a cross-sectional end view of the assembled insulated flexible air duct;

Figure 5 is a cross-sectional side view of the assembled insulated flexible air duct; and

Figure 6 is a perspective front view of the assembly device.

Detailed description of the embodiments

The prior art processes require fibrous insulation to be supplied in the required end-product thickness, therefore multiple thicknesses of insulation will be required to cater for the full range of available ducts.

The present invention aims to solve the earlier mentioned challenges by running a single insulation blanket specification for all duct sizes and thicknesses. This allows the fibre processing to be optimized for a single blanket type, with very low variability, high quality, and reduced maintenance down-time. The use of a single blanket dramatically improves the production scheduling capability as the availability of a specific type of insulation blanket no longer determines which duct types can be produced. The production of blanket in-house eliminates the freight costs of transporting blanket. Warehousing requirements are dramatically improved by allowing a shift to "last in-first out" stock control, thereby increasing the usable warehouse space, rather than needing access to many blanket types.

The proposed process splits the production of inner core, insulation application, and outer sleeve application, thereby eliminating some of the process complexities. If all three processes are combined, the process speed is governed by the speed of the slowest operation. For example, it may be possible to produce inner core at twice the speed that insulation can be applied, but the core operation must be slowed to match the speed of the insulation applicator. If there is any down-time, such as the need for machine maintenance or operator unavailability, then the entire process is stopped. In theory, a single pass process provides the lowest cost production if it can be optimised and run continuously. In practice, there are many factors that can potentially disrupt the process, thereby diminishing some of the benefits of a continuous process. Splitting the processes therefore allows each individual process to be optimised. A further benefit of splitting the processes is that a significant buffer of inner core can be established, providing improved production scheduling and process reliability. A further advantage is that duct core is frequently sold un-insulated for ventilation applications, which would require a dedicated core process regardless of whether a single-pass process was implemented.

According to the present invention, a method for manufacturing flexible insulated air ducts 10 includes the standard production of an inner core 12, with the novel aspects of the method lying in the application of the insulation layer. The insulation delivery mechanism (not shown) sits adjacent to the inner core 12, with the insulation strip 14, typically referred to as blanket fibre, being delivered substantially at right angles to the longitudinal axis A of the inner core 12, with provision for adjustment of the angle to provide accurate delivery of the insulation strip 14 onto the inner core 12.

The inner core 12 then rotates around its longitudinal axis A, thereby causing the insulation strip 14 to wrap around the inner core 12, which is delivered by a driven strip delivery process to maintain a consistent and controlled strip delivery rate. While rotating, the inner core 12 moves along the axial direction for the full length of the duct 10, which is typically 6 metres, thereby helically encasing the full length of the inner core 12 with multiple layers 16 of insulation strip 14. Some adhesives may be applied to the insulation to prevent adjoining layers 16 sliding. The relative speed of the inner core 12 rotation and the axial linear motion determines the amount of overlap, or helical pitch, of the insulation - slow linear motion results in high overlap. A thin insulation strip, in the range of 10mm to 15mm, but typically around 12mm in thickness, will be used such that many layers 16 will be typically required. For example, some duct with a low thermal rating may require as little as 3 or 4 layers 16, but high R-value duct may require up to 10 layers. The proportion of "overlap" relative to "blanket width" is related to the helical pitch, so that, for example, a duct with 5 layers of blanket will have an overlap of around 80% of the blanket width, which is typically in the range of 400mm to 600mm. This is in sharp contrast to the Adamczyk process which requires a single layer in which the overlap would be expected to be less than 10% of blanket width. The resulting fibre build up will produce a substantially homogeneous cylindrical tube of polyester fibre, without a substantial seam or join either along its longitudinal axis, as occurs with the use of traditional blanket, or helically around its circumference, as occurs with the Adamczyk process.

As shown in the Figures, the assembly device 30 includes a rear head assembly 32 and a front head assembly 34. The rear of the inner core 12 is pushed onto the three prongs 36 provided on the rear head assembly 32. The length of the inner core 12 is typically in the order of 6 metres and therefore it is compressed onto the rear head assembly such that the insulation applicator can be axially stationary. The front of the inner core 12 is attached to the front head assembly 34 and is dragged axially as the insulation strip is applied. The front and rear head assemblies 32,34 rotate in unison at a uniform speed.

As the inner core 12 rotates and is drawn out, a thin insulation strip 14 is feed to the inner core 12 in a direction substantially perpendicular to the central axis A, whilst being held at a constant tension. The insulation strip 14 helically overlaps multiple times around the inner core 12. The lateral portions 15 of the strip 14 at successive revolutions overlap consistently to create a continuous insulation layer. The speed of the rotation and axial movement of the inner core is set to provide the required overlap of the insulation strip for the requirements of the duct. A slow speed will result in more layers of the insulation strip being wound around the inner core, resulting in a greater overall thickness of the insulation layer, with up to ten layers being wound around. Faster speed would result in fewer layers, such as three layers of overlap.

As the insulated core progresses it is held by a curved tray 40. Once the inner core 12 has been fully wound by the insulation strip 14, an outer layer 42 is applied over the insulation layer. This may occur, as illustrated in Figures 2 and 3, by sliding a sleeve over the top of the insulated core. However, it will be appreciated that the outer layer may be applied by helically winding an outer strip about the insulated core using a similar process as is used for winding the insulation strip.

There are four benefits of providing a high overlap and "building up" the insulation: the outer surface 20 of the duct 10 will be substantially smooth with minimal corrugations in contrast to the Adamczyk process; the high overlap guarantees that there will be no gaps formed when the duct is bent on the outer surface of the bend, unlike the risk of gaps forming in the Adamczyk process, or the risk of openings forming between adjacent tubes in the Donnelly or Nova-Duct processes; the large amount of contact surface area between adjoining fibre layers will assist adhesion and restrict adjoining layers from shearing, thereby maintaining insulation integrity when it is subjected to tension through bending, thereby maintaining a substantially homogeneous tube of fibre; the rated thermal resistance can be adjusted easily through the control system and readily altered without loss of quality or the need for multiple adjustments or changes to raw material.

The insulated core is covered in a outer layer, or vapour barrier, 22, which is typically polyethylene or metalised PET, which can be overlaid in a variety of manual or automated processes.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

1. A method of manufacturing an insulated flexible air duct, including: providing a cylindrical inner core having a central axis; rotating the inner core about its central axis; feeding a strip of insulation material to the inner core, in a direction substantially perpendicular to the central axis of the inner core, whilst the inner core traverses in the axial direction thereby helically overlapping multiple layers of the insulation strip whereby lateral portions of successive revolutions overlap to create a continuous insulation layer around the inner core, such that the continuous insulation layer is built up by the multiple layers of insulation strip in any location along the length; wherein the speed of rotation and/or speed of axial traversal is able to be altered to provide the desired overlap distance of said lateral portions to create the required overall thickness of the insulation layer from multiple layers to meet the insulation requirement of the individual duct being manufactured; and applying an outer layer over the insulation layer.

2. A method according to claim 1, wherein the thickness of the insulation strip is the same for all duct sizes and insulation requirements, with the amount of overlapping providing the overall thickness of the insulation layer.

3. A method according to claim 1 or 2, wherein at least three layers of insulation strip are wound around the inner core in any one location along the length,

4. A method according to claim 1, 2 or 3., wherein the angular direction of the insulation strip with respect to the central axis of the inner core is adjustable to alter the pitch of the helical windings.

5. A method according to any one of the preceding claims, wherein the outer layer is provided by feeding the insulated core through a sleeving process whereby the insulated core is covered by a continuous sleeve layer.

6. A method according to any one of the preceding claims, wherein a layer of adhesive is applied to the insulation strip at the overlapping portions.

7. A method according to any one of the preceding claims, wherein the cylindrical inner core is produced completely independently of the process for the application of the insulation layer.

8. A method according to any one of the preceding claims, wherein the inner core initially sits compressed between a rear head assembly and a front head assembly, whereby the rear and front head assemblies rotate in unison, the rear head assembly does not move in the axial direction, and the front head assembly slides away from the rear head assembly dragging the inner core axially, extending it as the insulation strip is wound about it

9. An insulated flexible air duct made in accordance with the method of any one of claims 1 to 8.

10. An insulated flexible air duct, including: a cylindrical inner structural core; a continuous insulation layer created from helically wound and overlapping layers of a thin insulation strip whereby lateral portions of successive revolutions overlap to create the continuous insulation layer around the inner core; and an outer protective layer covering the insulation layer; wherein said overlapping lateral portions constitute a substantial portion of the width of the insulation strip, such that there are multiple layers of insulation strip at any given point along the length of the duct.

11. An insulated flexible air duct according to claim 9 or 10, wherein the number of layers of insulation strip around the inner core is determined by the helical pitch of the insulation strip, which determines the resulting thickness of the insulation layer.

12. An insulated flexible air duct according to any one of claims 9, 10 or 11, wherein the outer layer is a vapour jacket.

13. An insulated flexible air duct according to any one of claims 9 to 12, wherein the lateral portions of the insulation strip are bonded together.

14. An insulated flexible air duct according to any one of claims 9 to 13, wherein the insulation strip is a glass fibre insulation blanket.

15 . An insulated flexible air duct according to any one of claims 9 to 14, wherein the width of the insulation strip is in the range of 400mm to 600mm.

16. An insulated flexible air duct according claim 15, wherein the width of the insulated strip is 500mm.

17. An insulated flexible air duct according to any one of claims 9 to 16, wherein the thickness of the insulation strip is in the range of 10mm to 15mm.

18. An insulated flexible air duct according to claim 17, wherein the thickness of the insulation strip is 12mm.

19. An insulated flexible air duct according to any one of claims 9 to 18, wherein the overlapping lateral portions constitute between 60-80% of the width of the insulation strip.

20. An insulated flexible air duct according to any one of claims 9 to 19, wherein there are at least three layers of insulation strip at any given point along the length of the duct.